The present invention relates to a resin multilayer molding method and a multilayer molding device in which a skin material having a resin decorating layer on a surface and a core-material resin are integrally molded in a mold.
Recently, for resin molded products for use in automobile, household appliances, building materials, and the like, in order to enhance a surface decorative quality by applying added values such as decorativeness, good feel, cushioning properties, and the like and to reduce costs by saving molding processes, resin multilayer molding has been performed in which a decorating skin material having surface decorating performance such as the decorativeness, the good feel, the cushioning properties, and the like is integrally formed on a surface of a core resin using injection molding or press molding as described later in a mold simultaneously with molding of the core resin.
After the decorating skin material is set between opened mold pieces, in a clamped sate in which a clamping force is exerted by closing the mold or in a clamped state in which a specified mold open quantity is kept between the mold pieces, a mold cavity space formed by the decorating skin material and the mold is filled with a core material or molten resin by an injection device, a resin supply unit, or the like. After the filling of the core-material resin, the mold is loaded with a follow-up pressure by the injection device or the clamping device to integrally mold the decorating skin material and the core-material resin, and the mold is opened after an elapse of a predetermined cooling time to take a molded product therefrom.
However, the decorating skin material is largely damaged by loading of high temperature and pressure by the core-material resin from when the mold is filled with the core material or molten resin till the mold is opened to take out the molded product. A problem is caused that even when the decorating skin material with a foaming layer laminated on its back surface is used aiming at, for example, softness and cushioning properties, the foaming layer collapses during molding, and the softness, the cushioning properties, or another expected surface decorating performance cannot be obtained.
Another problem is caused that even when the decorating skin material provided with a gigging layer on its surface is used aiming at, for example, good feel and high grading, the gigging layer falls during molding, and the good feel, the high grading, or another expected surface decorating performance cannot be obtained.
Further problem is caused that even when the decorating skin material with a printed or painted layer laminated on its surface is used aiming at, for example, decorativeness or painting properties, microfine scratches made in the manufacture process of the skin material or microfine strains made at the time of deformation along a mold configuration during molding cannot be avoided, which results in surface defects such as tarnish, color shading, and the like. The decorativeness, the painting properties, or another expected surface decorating performance cannot be obtained.
As aforementioned, even when the decorating skin material is used for the purpose of enhancement of the added values such as decorativeness, good feel, cushioning properties, and the like, the originally targeted surface decorating performance cannot be obtained.
Means for solving the above-mentioned problems include a method in which a decorating skin material with a film having heat/pressure resistance or another protective layer laminated thereon is used. The method is designed to moderate influences of heat and pressure loads from the core-material resin during molding with the protective layer, but the manufacture cost of the decorating skin material is increased, the decorating skin material is only incompletely protected, and the target surface decorating performance cannot be satisfied.
As another means for solving the above-mentioned problem, in the case where the printed or painted layer is laminated on the surface of the decorating skin material aiming at decorativeness and painting properties, the decorating skin material is outlined/performed into a molded product configuration at a high temperature before molding. In this method, in the preforming process at the high temperature, the microfine scratches made in the manufacture process of the skin material or the microfine strains made at the time of deformation along the mold configuration during molding can be avoided to some degree, but incompletely. Furthermore, since the preforming process is added and a separate preforming facility is necessary, the cost of resin multilayer molding and the space for performing the molding are increased.
As new means for solving the above-mentioned problems, Japanese Patent Application Laid-open No. 150740/1984 proposes a low-pressure molding method in which the pressure loaded to the decorating skin material is minimized during the resin multilayer molding using press molding. Moreover, for example, Japanese Patent Application Laid-open No. 297489/1994 proposes a molding method in which the temperature of core-material molten resin is lowered, the pressure loaded on the decorating skin material is reduced, and the product of the pressure loaded on the decorating skin material during molding and pressure loaded time is further minimized. Both proposals are designed to suppress the damage of the decorating skin material being molded by reducing influences of pressure and heat loaded on the decorating skin material.
However, even if the damage of the decorating skin material can be suppressed by reducing the pressure loaded on the decorating skin material or reducing the product of pressure and time, a moldable, necessary minimum pressure exists for molding of the core-material resin. Consequently, a shortage of molding pressure of the core-material resin causes deformation, warpage, short shot, or other molding defects in view of products.
Moreover, in the method in which the temperature of the core-material molten resin is lowered, since the fluidity of the core-material resin is extremely lowered, the pressure at the time of molding of the core-material resin is extremely lowered, the pressure at the time of molding of the core-material molten resin (filling and flowing pressures) is inevitably enlarged, and the pressure loaded on the decorating skin material fails to drop. As a result, the molding method is a contradictory (actually invalid) proposal. Even if the method can be realized, the shortage of molding pressure of the core-material resin causes deformation, warpage, short shot, or other molding defects in view of products.
To perform molding by minimizing the loaded pressure and heat influences is certainly desirable in order to control the damage of the decorating skin material during molding, but this is a molding condition in which molding cannot be performed in view of the moldability of the core-material resin. Specifically, in the resin multilayer molding of resin using the decorating skin material, contradictory molding controls for preventing the decorating skin material from being damaged and for enhancing the moldability of the core-material resin have to be simultaneously performed during molding. Not only in the case where the conventional injection molding and press molding are used, but also in the molding control simply using the proposed low-pressure molding, molding cannot be performed with both controls being compatible.
Therefore, an object of the present invention is to provide a resin multilayer molding method and a multilayer molding device which can solve the conventional problems described above.
Another object of the present invention is to provide a resin multilayer molding method and a multilayer molding device which can supply remarkably high-quality resin multilayer molded products stably at low cost without impairing surface decorating performance.
According to the present invention, it is provided a resin multilayer molding method in which a skin material having a resin decorating layer on a surface and a core-material resin are integrally molded in a mold, comprising the steps of:
presetting a relationship of a glass transition point (Tgs) of the resin decorating layer of the skin material and a temperature (Tc) of a supplied molten resin forming a core material to satisfy Tgs less than Tc, and molding a molten resin and the skin material under a condition that a maximum temperature (Tsm) of the resin decorating layer of the skin material during mold clamping satisfies Tsm greater than Tgs; and
making a gap between the resin decorating layer of the skin material and a mold cavity surface opposed to the resin decorating layer to form and retain an air insulating layer therebetween, at a time when a temperature of the resin decorating layer of the skin material reaches a point within a preset value which is so estimated that a temperature (Tsc) which the resin decorating layer of the skin material reaches as a result of raising again after forming an air insulating layer satisfies Tscxe2x89xa7Tgs based on a relative between a temperature of the molten resin forming a core material and a temperature of the resin decorating layer of the skin material during the formation and the retention of the air insulating layer as well as clamping.
A technical concept of the present invention is hereinbelow described. In the present invention, a resin decorating layer damaged during clamping is recovered by elastic force of the resin in the same mold. That is, for recovering the damaged resin decorating layer by elastic force of the resin, it is necessary to make a temperature of the resin decorating layer higher than the maximum temperature which the resin decorating layer reaches during clamping under the condition that a clamping force is eliminated and a recovery space (gap) for the damage between the resin decorating layer and the mold cavity surface opposed to the resin decorating layer is retained. Heat transfer between the metal-mold cavity surface on the side of the resin decorating layer and the resin decorating layer is intercepted by arranging the above recovery space during cooling the core material resin, and heat-removing of the resin decorating layer from the mold almost stops. On the other hand, the core-material resin still has sufficient heat capacity, and the resin decorating layer is heated again to reach a temperature higher than the maximum temperature which the resin decorating layer reaches during mold clamping. Therefore, the resin decorating layer damaged during clamping can be self-restored by elastic force of the resin. That is, the maximum characteristic of the present invention is that a temperature of the resin decorating layer rises again by providing a gap of a mold during molding after the completion of clamping and reaches within a range where a damage caused during clamping can be self-restored by elastic force of the resin.
As described above, the present invention is a very inovational invention wherein opposite molding controls for increasing clamping ability of the core-material resin and for preventing damages on a decorative skin material can be simultaneously performed by separating a clamping process and a damage recovery process of a decorative skin material in resin multilayer molding in which a skin material having a resin decorating layer on a surface and a core-material resin are integrally molded in a mold.
The present invention can be also conducted by the use of a temperature of the core-material resin instead of a temperature of the skin material having a resin decorating layer (hereinbelow referred to simply as xe2x80x9cskin materialxe2x80x9d). That is, a correlation between a temperature of the core-material resin during clamping and forming and retaining the air insulating layer and a temperature of the skin material (corresponding to FIG. 3 of Japanese Patent Application 9-193889) is determined in advance, and a timing of forming the air insulating layer can be controlled by the use of a temperature of the core-material resin instead of a temperature of the resin decorating layer of the skin material. Further, a timing of forming the air insulating layer can be controlled on the basis of the time elapsed from a datum point from a correlation between the temperature of the core-material resin and the temperature of the skin-material decorating layer. That is, the estimation of this timing can be achieved, for example, by predicting how long it takes from the initiation of injection until the temperature of the skin-material decorating layer reaches aimed range from the above-mentioned relation.
The aforementioned explanation is on the best embodiment which completely recovers a damaged skin material. Further, an effective range of the present invention is not limited to the aforementioned range. That is, a considerable effect (a damage can be recovered) is obtained if a temperature of the skin material increases to a glass transition point or higher by providing an insulating layer even if the temperature of the skin material does not reach the maximum temperature which the skin material reaches during clamping. Further, it shows an effect of recovering a damage if a temperature of the skin material after rising again is near the glass transition point even if the temperature is lower than the glass transition point.
In the present invention, a molded article having a faithfully transcribed mold cavity surface on a surface of the skin material can be obtained by closing the mold to eliminate the air insulating layer and retained under pressure within a temperature range in which the temperature (Tsc) of the resin decorating layer of the skin material satisfies Tscxe2x89xa7Tgs at a preset arbitrary time after the air insulating layer is formed. That is, Tsc receives heat from the core resin during clamping and rises. However, when the temperature becomes higher than a temperature of the mold, heat transfer to the mold starts. Therefore, Tsc does not rise far above the temperature of the mold. This tendency is more remarkable on the surface which directly contacts the mold cavity surface than the other portions. On the other hand, since Tsc after the air insulating layer is formed retains the heat received from the core resin, Tsc rises almost independently of the temperature of the mold. Therefore, by being pressed with the mold being closed subsequently, transcription properties can be greatly improved since the mold cavity face is transcribed at a high temperature. In this case, since the mold cavity opposed to the skin material has an insulating structure, it is possible to maintain a temperature upon transcription from the beginning of pressing operation to the completion to be high, thereby giving a more preferable result. Since a temperature of the core resin is higher when the air insulating layer is formed in an earlier time in this molding method, Tsc after the insulating layer is formed also reaches high temperature, which is preferable for transcription. Because of this, it is preferable to arrange an air insulating layer at the time when filling of the resin in the cavity is completed independently of a temperature during clamping. Though the molded article is deformed by opening of the mold in this case, it does not cause any problem because the deformation is corrected by the clamping of the mold thereafter. In a molded article obtained by a method, a mirror polished surface without blur is faithfully transcribed when the cavity surface is a mirror polished, and a pattern of grain is faithfully transcribed when the mold cavity surface has grain.
Moreover, according to the present invention, it is provided a resin multilayer molding method in which a skin material having a resin decorating layer on a surface and a core-material resin are integrally molded in a mold, comprising the steps of:
at a preset arbitrary time after a molten resin forming a core material is supplied, and heating the resin decorating layer of the skin material up to the temperature Tgs or higher by using heating means incorporated inside the mold, or attached to the outside of the mold, or heating the resin decorating layer of the skin material to a glass transition point (Tgs) or a higher temperature by using a heating means incorporated inside the mold or a heating means attached outside the mold, and subsequently making a gap between the resin decorating layer of the skin material and a mold cavity face opposed to the resin decorating layer to form an air insulating layer, or forming the air insulating layer and subsequently heating the resin decorating layer of the skin material to Tgs or a higher temperature, or heating and simultaneously forming the air insulating layer, to retain the air insulating layer.
In the multilayer molding method, after the air insulating layer is formed, the resin decorating layer is heated up to Tgs or more using the heating means incorporated inside the mold or the heating means attached outside the mold, and then within a temperature range in which a temperature (Tsc) of the resin decorating layer of the skin material satisfies Tscxe2x89xa7Tgs at a preset arbitrary time, the mold is preferably closed to eliminated the air insulating layer and retained under pressure, which gives a molded article having a faithful transcription of a mold cavity face on the surface of the skin material.
Additionally, in a case where injection molding is used as the molding method, after an injection filling condition for injection filling the molten resin forming the core material into a mold cavity space and refilling a cooling/setting shrinkage quantity, a clamping condition during injection filling, the thickness of the air insulating layer, a change-over timing condition for forming the air insulating layer, and a change-over timing condition for eliminating the air insulating layer are initially set as molding condition, trial molding and visual quality determination by an operator are performed. In a case where the molding conditions need to be changed based on visual quality determination results, the molding conditions are preferably corrected using a prepared correction program to set optimum molding conditions for preventing the resin decorating layer of the skin material being molded from being damaged.
Moreover, in the present invention, after the injection filling condition for injection filling the molten resin forming the core material into the mold cavity space and refilling the cooling/setting shrinkage quantity, the clamping condition during injection filling, the thickness of the air insulating layer, the change-over timing for forming the air insulating layer, the change-over timing for eliminating the air insulating layer, and a heating condition for using heating means to heat the resin decorating layer of the skin material are initially set as molding conditions, the trial molding and the visual quality determination by the operator are performed. In a case where the molding conditions need to be changed based on visual quality determination results, the molding conditions are preferably corrected using the prepared correction program to set optimum molding conditions for preventing the resin decorating layer of the skin material being molded from being damaged.
Furthermore, in the present invention, it is preferable that a minimum thickness (Lm) of the resin decorating layer of the skin material being molded, a thickness (Lf) of the resin decorating layer after molding which satisfies the required surface decorating performance of a multilayer molded product and a thickness La of the air insulating layer have a relationship Lfxe2x88x92Lmxe2x89xa6La.
Moreover, in the present invention, the skin material is preferably a lamination of a resin decorating layer which is formed by laminating a surface decorating layer portion constituted of a resin film, a resin woven fabric, a nonwoven fabric made of polymer fiber singly or in a combined manner and an intermediate decorating layer portion constituted of a foaming resin on a back surface of the surface decorating layer portion as needed in accordance with a surface decorating purpose, and a base layer constituted of a resin film, a woven fabric or a nonwoven fabric or a combination thereof as needed.
Additionally, it is preferable that the temperature of the core-material resin and the temperature of the resin decorating layer of the skin material during molding are detected, while the change-over timing for forming the air insulating layer and the change-over timing for eliminating the air insulating layer are controlled with a detected temperature signal.
Furthermore, the change-over timing control for forming the air insulating layer and the change-over timing control for eliminating the air insulating layer are preferably performed with a time-out signal of a timer which starts at an arbitrary time during molding.
Still furthermore, the correction program is preferably provided with a function of selecting an item required to be corrected from the initially set molding condition values based on the present correction direction and quantity corresponding to an quality defect item and a quality defect degree which are obtained from operator""s visual quality determination results; a function of correcting the set value of the selected set item; and a function of issuing an operation command for changing supplementary molding conditions constituted of a mold temperature, a core-material resin temperature, and the like, when the corrected set value reaches a preset critical correction value.
In the present invention, the mold with an insulating cavity layer formed on the mold cavity surface opposed to the resin decorating layer of the skin material may be used.
The present invention also provides a resin multilayer molding device in which a skin material having a resin decorating layer on a surface and a core-material resin are integrally molded in a mold, comprising:
carrying means for carrying and setting the skin material to a predetermined position of a mold cavity and carrying a molded product to a predetermined position after molding, and supply means for supplying a molten resin forming a core material into a mold cavity space; and
a clamping condition setting section for setting/entering a clamping condition and a thickness of an air insulating layer during supply and after supply of the molten resin, a change-over timing setting section for a change-over timing condition for forming the air insulating layer and a change-over timing condition for eliminating the air insulating layer, a temperature detecting section for detecting a temperature of the core-material resin and a temperature of the resin decorating layer of the skin material during molding, a comparison control section for comparing/determining a detection signal of the temperature detecting section and a set value of the change-over timing setting section, and a clamping control section for controlling clamping means based on a signal of the comparison control section and a set value of the clamping condition setting section.
Furthermore, the present invention provides a resin multilayer molding device in which a skin material having a resin decorating layer on a surface and a core-material resin are integrally molded in a mold, comprising:
carrying means for carrying/setting the skin material to a predetermined position of a mold cavity and carrying a molded product to a predetermined position after molding, and supply means for supplying a molten resin forming a core material into a mold cavity space; and
a clamping condition setting section for setting/entering a clamping condition and a thickness of an air insulating layer during supply and after supply of the molten resin, a heating temperature condition setting section for setting a temperature to which the resin decorating layer of the skin material is heated, a heating temperature detecting section for detecting the heating temperature of the resin decorating layer of the skin material, heating means for heating the resin decorating layer of the skin material based on a set value of the heating temperature condition setting section and a detection signal of the heating temperature detecting section, and a clamping control section for controlling clamping means based on a set value of the clamping condition setting section.
The above-mentioned multilayer molding device is preferably when an injection molding device is employed.
The multilayer molding device equipped with the injection molding device preferably includes an initial setting input section for initially setting/entering as molding condition values an injection filling condition for injection filling the molten resin forming the core material into the mold cavity space and refilling a cooling/solidification shrinkage quantity, a clamping condition during the injection filling, a thickness of the air insulating layer, a change-over timing condition for forming the air insulating layer and a change-over timing condition for eliminating the air insulating layer; a molding device control section for operating/controlling the multilayer molding device for performing resin multilayer molding based on set values of the initial setting input section; a quality determination input section for entering visual quality determination results; and a correction program storage section for storing a correction program for correcting the initially set molding condition values based on input values of the quality determination input section to set optimum molding conditions for preventing the resin decorating layer of the skin material being molded from being damaged.
Moreover, the multilayer molding device preferably includes an initial setting input section for initially setting/entering as molding condition values an injection filling condition for injection filling the molten resin forming the core material into the mold cavity space and refilling a cooling/setting shrinkage quantity, a clamping condition during the injection filling, a thickness of the air insulating layer, a change-over timing condition for forming the air insulating layer, a change-over timing condition for eliminating the air insulating layer, and a heating condition for heating the resin decorating layer of the skin material using heating means; a molding device control section for operating/controlling the multilayer molding device for performing resin multilayer molding based on set values of the initial setting input section; a quality determination input section for entering visual quality determination results; and a correction program storage section for storing a correction program for correcting the initially set molding condition values based on input values of the quality determination input section to set optimum molding conditions for preventing the resin decorating layer of the skin material being molded from being damaged.
Furthermore, the multilayer molding device preferably includes a timer which starts at an arbitrary time during molding, and a change-over timing setting section for setting the change-over timing condition for forming the air insulating layer and the change-over timing condition for eliminating the air insulating layer in response to a time-out signal of the timer, and means for forming the air insulating layer may be incorporated in the mold. Additionally, an insulating cavity layer may be formed on a cavity surface opposed to the resin decorating layer of the skin material.
Furthermore, in case of the present inventive, device a conventional known method can be applied as the molding method, and injection molding, press molding, blow molding, vacuum molding and other various molding methods can be used. Among the methods, the injection molding and the press molding are preferable.